Rheostat



Aug 28, 1

Original Filed Jan. 23, 1932 mmm? Patented Aug. 28,v 1934 .UNITED smits PATENT lorifice A Cutler-Hammer, Inc., poration of Delaware Application January 23, 1932, Serial No.,

Milwaukee, Wis., a cor- Renewed April 23, 1934 12 Claims.

This invention relates to improvements in rheostats and more particularly to combined switch and rheostat devices for speed control of electric driving motors of fractional horsepower.

An object of the invention is to provide a small and compact-rheostat adapted for one-hole mounting.

Another object is to provide novel means for retaining the resistance elements in asl@ semble-id relation 'to the insulating supporting base.

Another object is to provide a novel form of bridging contacter for cooperation with the resistance elements of the device.

Another object is to provide a novel arrangement of the casing parts whereby proper ventilation or cooling of the resistance elements is insured. v

Another object is to provide a novel connection between the insulating knob and metal shaft oi' the device.

Another object is to generally improve the details of construction and arrangement of thev various parts of a device of the character aforementioned.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that the invention is susceptible of embodiment in other forms without departing from the scope of the appended claims.

In the drawing, Figure 1 is a perspective view, in separated relation, of the several parts of a rheostat constructed in accordance with my invention.

Fig. 2 is a top plan view of the rlieostat, the casing and other of the parts being broken away lo to show the contactor in its off position.

Fig. 3 is a vertical sectional view on the line 3-3 of Fig. 2.

Fig. 4 is a bottom plan view of the rheostat illustrating the manner of attaching the casing L5 to the insulating base.

Fig. 5 isa view taken on line 5-5 of Fig. 2, but showing the contactor in bridging engagement with the resistance elements, and

Fig. 6 is a sectional view on line 6-6 of Fig. 10 3,-illustrating the manner of attaching the insulating knob to the actuating shaft.

Referring to the drawing. the numeral 10 designates a base of substantially circularcontour molded from a suitable insulating material. 5 Said base is provided in its upper face with a (Cl. 20L-56) centrally located cylindrical recess l1 and a pair of segmental grooves l2 and 13 arranged concentrically with respect to recess ll, said grooves as shown each extending through an are of substantially less than l. @0

Grooves 12 and 13 are provided at diametro cally opposed ends thereof with enlargements or recesses le and l5 respectively-passages 14.a and 15e being provided which open to the recesses 1o and 15 and to the bottom face or base 1o. @5 Grooves 12 vand i3 are provided at the other ends thereof with vertical-shoulders l2n and 13a for a purpose to be described.

Surrounding recess l1 is an annular dat portion 1'8 and arranged in the plane of the latter and in 7@ diametrically opposed relation to each other are a pair of segmental surfaces 19 and 20,-the segmental surfaces 18b being arranged in a plane offset downwardly with respect to portion 18, and inclined surfaces or portions la 4being lo- 75 cated therebetween.

Base 10 is provided with a peripheral ledge 21 which forms a seat for the metal cover or casing 37 as hereinafter described-said ledge being interrupted at a plurality of points by the grooves or passages 22 which open to relatively large recesses 22a on the bottom surface of base l0. Ledge 21 is also provided with a plurality of depressed or downwardly offset portions 2l which cooperate with the cover or housing 37 to afford 85 Ventilating passages, as hereinafter more fully described.

The resistance elements comprise a pair of helically wound wires 23 and 24, the end coils 23.a and 24 of which are bent as shown to lie in the 90 plane of the bottom surfaces thereof respectively. Said end coils 23 and 24a are inserted into the recesses 14 and 15 and are adapted to be retained in the latter by the heads of screws 25 and 26 the shanks of which penetrate passages 14B and 15B 95 and take into the tapped openings in nuts 27,- the latter being restrained from rotation by the side walls of recesses 14b and 15b in the lower face of base 10. Nuts 28 are also provided for cooperation with nuts 27 to clamp suitable circuit 100 wires (not shown) in position. The helices 23 and 24 are lightly pressed downwardly to conform to the shape of the segmental grooves 12 and 13 and to seat within the latten-said helices also, if desired, `being of such length as to require slight compression thereof endwise by the assembling operation to lnsur frictional engagement of the free end portions thereof with the vertical shoulders 12B and 13a of said grooves.

The bridging contactor comprises a punched andgstamped sheet metal member 29 having a centrally located elongated opening 30. Member 29/is` provided at opposite ends thereof with relatively narrow outwardly projecting arms 31 and 32 which are odset upwardly from the main body of said member, said arms respectively having pairs of upwardly extending parallel lugs 31 and 32B. Said pairs of lugs 31EL and 32a are adapted to receive therebetween the relatively narrow projections 33 and 34 formed integrally with the flat punched plate 35 of insulating material,- said plate being of substantially circular contour, and of a size to partially overlie the resistance elements 23 and 24. Plate 35 is provided with a centrally located elongated opening 36 registering with, but considerably smaller than, opening 30 in member 29. Member 29 is further provided on its lower surface with diagonally positioned bosses or projections 29 and 29h. as shown.

Rigidly secured to base 10' in a well known manner as by means of integral lugs 37 adapted to register with grooves 22 in the periphery ofbase 10 and bent inwardly over the bottom surface of recesses 22H, is a substantially dome-shaped metal casing or housing A37, the bottom edge of said housing being adapted to seat upon the ledge 21 aforementioned. Housing 37 is further provided with a central opening 38, preferably of polygonal contour, and a plurality of circular openings 39 are arranged symmetrically thereabout. Central opening 38 is adapted to receive the reduced lower end 41 of an externally threaded hollow metal bushing 40, said end 41 being upset over the inner surface of housing 37 to rigidly and permanently secure said bushing and housing to each other. Openings 39 and the gaps formed by cooperation of the depressed portions 21 of ledge 21 with housing 37 (Fig. 3) as aforementioned provide plural passages for convection currents of cooling air around and about the resistance elements when the latter are rendered active.

Rotatable within the bushing 40 is an actuating shaft 42 which preferably consists of a fiat sheet metal punching having a pair of lateral projections or arms 43 and 44 which are adapted to bear against the lower end surface 45 of the bushing. One end 46 of the shaft projects upwardly beyond the bushing and is adapted to have fitted thereonto a knob 47 preferably molded from a suitable insulating material. Knob 47 is provided with a recess 48 of rectangular cross section,-end 46 having a drive fit within said recess as best illustrated in Figs. 3 and 6. The lower surface 49 of the knob is adapted to bear against thel upper end of bushing 40. Knob 47 is grooved as shown at 50, or otherwise roughened to facilitate manipulation thereof. As shown. the upper surface of the knob is preferably provided with an arrow 51 or other marking which may be utilized in conjunction with a panel or mounting board (not shown) having suitable legends thereupon, to indicate the position of the bridging contactor,it being understood that recess 48 is so formed and the knob so assembled with respect to shaft 42 as to provide forancl insure location of arrow 51 in the plane of the, width of said shaft.

The lower portion 52 of shaft 42 is adapted to extend downwardly through the opening 36 in plate 35 to afford a driving connection with the latter,it being noted that the opening 30 in contactor 29 is suflciently large to insure against contact of the latter with said. shaft. The lower portion 52 of the shaft is adapted to t loosely within the central recesses 11 in .base 10 to assist in centering said shaft with respect to said base. Interposed between the arms 43, 44 of the shaft and the upper surface of plate 35 is a coiled compression spring 54, said spring being compressed to a predetermined degree by assembly of the rheostat parts as aforedescribed. In-this manner the arms 31 and 32 of the contactor, are normally biased downwardly toward the resistance elements. Because of the substantial depth of grooves 12, 13 and the snug t of resistors 23,'24 8J therein there will be substantially no tendency for the free ends of said elements to twist or curl upwardly out of their respective assembled positions. Moreover, it will be noted that insulating plate 35 partially overlies the resistors (Fig. 2), thereby positively insuring against any substantial upward movement of said elements out of grooves 12, 13 and thus obviating the necessity for otherwise securing the free ends of said elements.'

Assuming off positioning of the contactor, as il- @l lustrated in Figs. 1, 2 and 3, it will be noted that the bosses 29B, 29b are engaged with the segmental. surfaces 19, 20; and upon a slight initial movement of knob 47 in a clockwise direction said bosses will simultaneously ride out of engagement 10i with surfaces 19, 20 to permit a quick downward movement of the contactor arms into engagement with those coils adjacent to the respective fixed ends of the resistors. In this manner I provide for initially subjecting the translating device l0! (such as a relatively small motor driving the fan of an automobile heater system) to the maximum value of current, whereby starting of the motor will be insured. If it is desired to decrease the value of currentsupplied to the translating delili vice this result may be obtained by merely continuing the movement of the knob in a clockwise direction. When the arms of the contactor reach the free ends of the resistors, said arms will engage the vertical walls 16B, i7a of the abutlili ments 16 and 17 formed integrally. with base 10, thereby insuring against interruption of the controlled circuit in this extreme position of the bridging contactor.

When it is desired to increase the value of cur- 112i rent supplied to the translating device knob 47 may be moved in a counterclockwise direction until the arms of the contactor overlie the coils closely adjacent to the respective xed ends of the resistors. At this moment the bosses 29e, 29b 12l will engage the shoulders 19e, 20a at the diagonally opposite sides of the segmental surfaces 19, 20 and continued counterclockwise movement of knob 47 will of course result in a rapid upward movement of the contactor arms out of engage- 13( ment with said resistors.

It will be noted that by the arrangement of parts as aforedescribed I4 provide for proper control of the amount of resistance to be included in the controlled circuit, while at the same time in- 131 suring a fairly rapid make and break of the controlled circuit at one extreme position of the contactor. In this manner arcing between the arms of the contactor and the resistors is effectually minimized. 14(

The bushing 40 is preferably provided with one or more clamping nuts 55, 56'(Fi'g. 3) whereby the rheostat is adapted for one-hole mounting in panels or mounting boards (not shown) of different thicknesses.

What I claim as new and desire to secure by Letters Patent is:

1'. In a rheostat, in combination, a pre-formed base of molded insulating material having a pair of grooves arranged substantially semi-circularly 15 in opposed relation to each other upon the upper surface thereof, a pair of self-sustaining helically woi'nd resistors iltting snugly within the respecti e grooves with the coils of the former under endwise compression, a one-piece sheet metal contactor extending diametrically across said base and having contact portions adapted for bridging. engagement with said resistors, an insulating member with which said contactor is loosely interconnected for-rotation thereby, said insulating member having portions thereof overlying said resistors in all positions of said contactor to assist in retaining said resistors in properly assembled relation to said base. a shaft with which said insulating member is slidably interlocked for rotation thereby, and a coiled compression spring interposed between'a portion of said shaft and said insulating member to yieldably bias said contactor into the plane of engagement of the latter with said resistors.

2. In a rheostat, in combination, a pre-formed base of molded insulating material having a pair of grooves arranged substantially semi-circularly in opposed relation to each other upon the upper surface thereof, a pair of self-sustaining helically wound resistors fitting snugly within the respective grooves with the coils of the former under endwise compression, a one-piece sheet metal contactor extending diametrically across said base and having contact portions adapted for bridging engagement with said resistors, an insulating member with which said contactor is loosely interconnected for rotation thereby, said insulating member having portions overlying said resistors in all positions of said contactor to assist in retaining said resistors in'properly assembled relation to said base, a shaft with which said insulating member is interloeked for rotation thereby, and a coiled compression spring interposed between a portion of said shaft and said insulating member to yieldably bias said contactor into the plane of engagement of the latter with said resistors, said insulating base and said contactor having cooperating parts formed integrally therewith respectively to positively lift the latter upwardly out of said plane of engagement during movement thereof to one extreme position.

3. In a rheostat, in combination, a pre-formed base of molded insulating material having a pair of grooves arranged substantially semi-circularly in opposed relation to each other upon the upper surface thereof, a pair of self-sustaining helically wound resistors fitting snugly within the respective grooves with the coils of the former under endwise compression, a one-piece sheet metal contaeter extending diametrically across said base and having contact portions adapted for bridging engagement with said resistors, an insulating member with which said contactor is loosely interconnected for rotation thereby, said insulating member having portionsoverlying said resistors in all positions of said contactor to assist in retaining said resistors in properly assembled relation to said base, a shaft with which said insulating member is interlocked for rotation thereby, and a coiled compression spring interposed between a portion of said shaft and said insulating member to yieldably biessaid contactor into the plane oi engagement of the latter with said resistors, said insulating base and said contactor having cooperating parts formed integrally therewith respectively to positively lift the latter upwardly out of said plane of engagement during movement thereof to one extreme position, said insulating base also having parts formed integrally therewith to positively limit movement of the respective contact portions through arcs of substantially less than one-hundred and eighty degrees.

4. In a rheostat, in combination, a pre-formed base of molded insulating material having a pair of grooves arranged substantially semi-circularly in opposed relation to each other upon the upper surface thereof, a pair of yself-sustaining helically wound resistors fitting snugly within the respective grooves with the coils of the former under endwise compression, a one-piece sheet metal contactor extendingdiametrically across said base and having contact portions adapted for bridging engagement withI said resistors, an insulating member with which said contactor is interlocked for rotation thereby, said insulating member having portions overlying said resistors in all positions of said contactor to assist in retaining said resistors in` properly assembled relation to said base, a shaft with which said insulating member is loosely interconnected for rotation thereby, a coiled compression spring interposed between a portion of said shaft and said insulating member to yieldably bias said contactor into the plane of engagement of the latter with said resistors, said insulating base having diametrically opposed projections of substantially triangular cross section formed integrally therewith to positively limit the respective contact portions to oscillatory movement through arcs of substantially less than one hundred and eighty degrees, and saidinsulating base and said contactor having projections formed integrally with the opposed faces thereof to insure positioning of said contact portions out of said plane of engagement in one extreme position of said contactor.

5. In a rheostat, in combination, a relatively small molded insulating base of substantially circular contour, said base having a pair of opposed substantially semicircular grooves formed in the upper face thereof, barriers formed integrally with said base between the adjacent ends of the respective grooves, said base having an enlarged recess formed at one end of each groove, said recesses being arranged in diametrically opposed relation `to each other, a pair of helically wound resistors fitting snugly within said grooves, each of said resistors having a coil at one end thereof bent downwardly to lie within the respective recess, a pair of screws the Shanks of which are respectively adapted to penetrate said end coils of said resistors and said base whereby the heads of said screws are adapted to clampingly engage said end coils within said recesses, nuts upon the lower face of said base with which said screw shanks are respectively adapted to engage, and additional nuts carried by said screw shanks to provide for attachment of circuit wires.

6. In a rheostat, in combination, a relatively I small molded insulating base of substantially circular contour, said base having a pair of opposed substantially semicircular grooves formed in `the upper face thereof, barriers formed integrally with said base between the adjacent ends of the respective grooves, said base having an enlarged recess formed at one end of each groove, said recesses being arranged in diametrically opposed relation l to each other, a pair of self-sustaining helically wound resistors fitting snugly within said grooves, terminal elements located within said recesses and electrically connected with the respective resistors, said terminal elements having wirey attaching means exposed upon the lower surface of said base, a contactor extending diametrically across said Aso base, said contacter in one extreme position being adapted to overlie the respective terminal elements whereby the former is'disengaged vfrom said resistors and said contacter being adapted in another extreme position te engage the remote ends of the respective resistors, means for moving said contacter to either of said extreme positions or to any intermediate position at will, said means comprising a punchd -plate of insulating material, said plate and said contacter having interitting parts to provide for driving of the latter by the former, a shaft having driving'engagement with said' plate, a coiled compression spring interposed between a portion of said shaft and said plate, a metal housing providinga bearing for said shaft, and lugs formed integrally with said housing to provide for attachment thereof to said base'.

7. In a rheestat for control of relatively low voltage circuits, in combination, a molded. insulating base having a pair of arcuate grooves in the upper face thereof, a pair of helically wound, self-sustaining resistors fitting snugly within said grooves and each having one end thereof rigidly attached to said base, wiring terminal elements exposed upon the bottom face of said base, an inverted cup-shaped sheet metal housing rigidly attached to said base, an externally threaded hollow metal bushing attached to the upper end of said housing, a flat punched sheet metal shaft located within said bushing, means on said shaft to bear against opposite ends of said bushing, a punched plate of insulating material slidably mounted upon said shaft but interlocked therewith for rotation thereby, a punched and stamped sheet metal contacter having a loose interlocking engagement with said plate for rotationthereby, and spring means interposed between a portion of said shaft and said insulating plate to bias the latter and said contacter toward said insulating base.

8. In a device of the character described, in combination, a punched and stamped sheet metal contacter comprising a body portion of substantially loop-shape, contact arms formed integrally with said body portion and offset upwardly from the plane of the latter, a pair of lugs formed integrally with each of said contact arms and bent upwardly therefrom in parallel relation toV each other, a punched insulating plate of approximately circular contour, said plate being cut away at diametrically opposite sides thereof to provide for accommodation thereof between the adjacent ends of said pairs of lugs, and said plate having projections formed integrally therewith to fit within the respective pairs of lugs for driving of said contacter, and associated means for driving said insulating plate.

9. In a device of the character described, in

Y combination, a punched and stamped sheet metal contacter comprising a body portion of substantially loop-shape, contact arms formed integrally with said body portion and offset upwardly from the plane of the latter, a pair of lugs formed integrally with each of said contact arms and bent upwardly therefrom in parallel relation to each other, a punched insulating plate of approximately circular contour, said plate being cut away at diametrically opposite sides thereof to provide for accommodation thereof between the adjacent ends of said pairs of lugs, and said plate having projections formed integrally therewith to t within the respective pairs of lugs for driving of said contacter, and associatedmeans for driving said insulating plate,`said contacter having bosses formed at diagonally opposite points inthe botrelation to each other, a pair of helically wound,

self-sustaining resistors fitting snugly within said grooves. wiring terminal elements mechanically and electrically connected to said resistors within said recesses and having portions thereof exposed upon the lower face of said base, and a bridging contacter. extending diametrically across the upper face of said base and osciilatable with respect thereto, said contacter having a single eff position wherein it overlies the respective recesses to disengage said resistors, said contacter being also movable unidlrectlonally from said off position to initially engage said resistors adjacent te the wiring terminal ends thereof and to thereafter traverse said resistors toward the remote ends thereof, whereby the value of resistance included 10o in circuit with said contacter is gradually increased.

1l. In a rheestat for control of relatively low voltage circuits, in combination, an insulating base, said base having a plurality of notches formed in the periphery thereof, an inverted cupshaped sheet metal housing having a multiplicity of Ventilating openings formed therein and having its lower edge` seated against the upper surface of said base, said housing having integral lugs located within said notches and bent into engagement with the lower surface of said base whereby said parts are retained in assembled relation, an externally threaded hollow metal bushing rigidly attached to said housing and projecting upwardly 115 therefrom, a metal -shaft penetrating said bushing and having portions projecting above and below the respective ends of the latter, a molded insulating knob having a recess within which said shaft is forcibly inserted to restrain said knob 12@ lli@ and said shaft against rotary and longitudinal movement relatively to each other, a fiat punched plate of insulating material with which the lower end of said shaft has driving engagement, a punched and stamped sheet metal contacter with which said insulating plate has driving engagement, a helically wound resistor supported upon the upper surface of said insulating base, a wiring terminal element with which one end of said resister is mechanically and electrically connected,

said terminal element being exposed upon the lower surface of said base, said contacter having a single off position wherein it overlies the aforementioned end of said resistor to disengage the latter, said contacter being also movable unidirectionally from said ofi' vposition to initially engage said resistor adjacent to the wiring terminal end of the latter and to thereafter traverse said resistor toward the remote end thereof, whereby the value of resistance included in circuit with said contacter is gradually increased, and a second .wiring terminal element with which said contacter is electrically connected under the conditions last mentioned.V Y

l2. In a rheostat for control `of relatively low voltage circuits, in combination, an insulating base having a groeve formed in the upper surface thereof, said base having a plurality of notches formed in the periphery thereof, an inverted cupshaped sheet metal housing having a multiplicity 150 of ventilating passages formed therein and having its lower edge seated against said upper surface of the base, said housing having integral lugs 1ocated within said notches and bent into engagement with the lower surface of said base whereby said parts are retained in assembled relation, an externally threaded hollow metal bushing rigidly attached to said housing and projecting upwardly therefrom, a metal shaft penetrating said bushing and having portions projecting above and below the respective ends of the latter, a molded insulating knob having a recesstoaccommodate the upper end of said shaft, said knob and said shaft being restrained against rotary and longitudinal movement relatively to eachother, a member or insulating material with which the lower end of said shaft has a driving connection, a punched and within said groove in the upper surface of said insulating base, a wiring terminal element with which one end of said resistor is mechanically and electrically connected, the other end of said resistor being unconnected electrically, said terminal element being exposed upon the lower surface of said base, said contactor being movable in one direction out of engagement with said resistor to a single oi position, said contactor being also movable in the reverse direction from said oi position to initially engage said resistor adjacent to the wiring terminal end of the latter and to thereafter traverse said resistor toward the remote end thereof, whereby the value of resistance included in circuit with said contactor is gradually increased, means for preventing disengagement of said contactor from said resistor upon movement thereof in the direction last mentioned, and a second wiring terminal element with which said contactor is electrically connected under the conditions last mentioned.

GEORGE J. MEUER. 

